1. Field of the Invention
The invention relates to water-dispersible and to organic solvent soluble polyesters and to their preparation and use, for example, as additives in coating compositions.
2. Description of Related Art
The process of electrodeposition coating has been found to be advantageous for the coating of metal panels. In the cataphoretic coating of zinc-coated metal panels with the binders conventionally employed, surface defects become evident in the baked film, especially at the relatively high deposition voltages which are required in order to achieve high coat thicknesses.
Patent application EP-A-0 569 842 describes urethanes which have the ability, when added to cationic electrodeposition coating baths (EDC baths), to prevent these phenomena. These urethanes are low molecular weight compounds and are therefore, subject to different approval regulations in different geographical states. The toxicological properties of such compounds are not entirely harmless. Furthermore, these urethanes are not of equal compatibility with all of the binders conventionally used. In the case of relatively thick coatings in particular, uneven distribution in the film may occur, which manifests itself likewise in the form of surface defects.